In current imaging systems using light valves each having an array of individually addressable pixels, color images are produced by field-sequential illumination techniques. For example, red, green, and blue colors of illumination light from an illumination system are sequentially incident onto the light valve. The light valve modulates different colors of light separately at different times; and the modulated colors of light are overlapped on a screen so as to form the desired color images on the screen. Due to the sequential illumination, illumination light of single color is incident to the light valve and arrived at the screen at a time; while other colors of light are blocked from reaching the light valve and the screen. As a result, the brightness of the produced color images on the screen is reduced.
Field-sequential illumination techniques may cause other problems, especially in imaging systems using solid-state illuminators such as lasers and light-emitting-diodes (LEDs). It has been observed that solid-state illuminators can output maximal light intensity when operated continuously; while the output light intensity may not be maximal at an intermittent mode. Therefore, when used with a field-sequential technique, the solid-state illuminators are operated at an intermittent mode, resulting in degraded output intensity, which in turn, degrades the brightness of the produced color images on the screen.